- Replace unicode text ('⛶', '×') with SVG icons for fullscreen/close buttons
- Add new SVG icons (windowMaximize, windowRestore, x) to icon_utils.js
- Update CSS selectors to scope window button styles under #model-linker-modal
- Remove border/box-shadow from buttons, add hover states
- Increase button size to 46x40px with full height
- Add aria-label attributes for accessibility
- Adjust dialog controls layout with stretch alignment